1. Field of the Invention
The present invention relates to a liquid supply system which uses a negative pressure to supply liquid to the outside, particularly to a liquid supply system in which the residual amount of liquid in a liquid container can be detected, and an ink jet recording apparatus.
2. Related Background Art
As a conventional liquid supply method in which a negative pressure is utilized to supply liquid to the outside, for example, an ink tank which gives the negative pressure to an ink discharge head has been proposed in an ink jet recording apparatus field, and a constitution (head cartridge) which can integrally be formed with a recording head has been implemented. Specifically, the head cartridge can further be classified to a constitution in which the recording and an ink tank (ink container) are constantly integrally constituted, and a constitution in which recording means is separate from the ink container, both can also be separated from a recording apparatus, and they are integrally combined during operation.
As one of easiest methods for generating the negative pressure in such liquid supply system, there is a method of utilizing the capillary force of a porous material. The ink tank in this method is constituted of a sponge or another porous material contained, preferably compressed/contained entirely in the ink tank for a purpose of ink storage, and an atmosphere connecting port via which air can be taken into the ink container to smooth the ink supply during printing.
However, as a problem when the porous member is used as an ink holding member, the ink containing efficiency per unit volume is low. To solve the problem, the present applicant has proposed an ink tank in the publication of EP0580433 in which the whole excluding a connecting portion to a negative pressure generating member containing chamber has a substantially sealed ink containing chamber and the negative pressure generating member containing chamber is opened to the atmosphere during operation. Moreover, in the publication of EP058531, for the ink tank structured as described above, the invention for a changeable ink containing chamber has been proposed.
In the above-described ink tank, since ink is supplied to the negative pressure generating member containing chamber from the ink containing chamber by a gas-liquid replacing operation of containing gas in the ink containing chamber with the introducing of the ink in the ink containing chamber, the ink can advantageously be supplied under a substantially constant negative pressure condition during this gas-liquid replacing operation.
Furthermore, in the publication of EP0738605, the present applicant has proposed a liquid container which comprises a substantially polygon columnar housing, and a containing portion which has the shape of an outer surface equal to or complementary to that of the inner surface of the housing and which can be deformed when the liquid contained inside is guided to the outside. For the thickness of the containing portion, the portion constituting a corner portion of each surface of the substantially polygon columnar shape set to be thinner than the center region thereof. In this liquid container, when the containing portion is appropriately contracted (gas-liquid exchange is not performed in phenomenon) with the introduced liquid, the liquid supply can be performed by utilizing the negative pressure. Therefore, the arrangement position is not limited different from the conventional bag-shaped ink containing member, and the container can be disposed on a carriage. Moreover, the invention is also superior in that since the ink is directly held in the containing portion, the ink containing efficiency is enhanced.
On the other hand, in order to prevent the ink from running out during printing operation in the ink jet recording apparatus, a residual ink amount detecting mechanism is requested to be mounted which detects the ink consumption condition or residual amount and which informs a user that the time to exchange the ink tank is coming.
Additionally, in the ink tank in which the above-described negative pressure generating member containing chamber is adjacent to the ink containing chamber, when the ink of the ink containing chamber having a predetermined fixed containing space is supplied to the negative pressure generating member containing chamber, gas-liquid exchange is performed to guide gas into the ink containing chamber.
Therefore, when the ink of the ink containing chamber is supplied to the negative pressure generating member containing chamber, the amount of outside air corresponding to the ink amount is accordingly introduced, and the outside air and the ink are present in the ink containing chamber. When the outside air swells by the change of environment in which a printer is used (e.g., a temperature difference in one day), the ink in the ink containing chamber is guided toward the negative pressure generating member containing chamber in some cases. Therefore, in conventional cases, by considering the ink movement amount to the swelling proportion with various operation environments, the maximum buffer space is secured for the negative pressure generating member for practical use.
Moreover, in the conventional gas-liquid replacing operation, the introducing of the ink to the negative pressure generating member containing chamber from the ink containing chamber is performed with the introduction of the outside air via the connecting portion. Therefore, when a large amount of ink is supplied to the outside (liquid discharge head, and the like) from the negative pressure generating member containing chamber in a short time, the ink supply to the negative pressure generating member containing chamber from the ink containing chamber by the gas-liquid replacing operation possibly becomes insufficient to rapid ink consumption in the negative pressure generating member containing chamber. Therefore, also to avoid the ink supply shortage, the condition of the ink in the ink containing chamber needs to be known.
To solve the above-described problems, some of the present inventors have analyzed in detail the situation of the ink containing chamber containing air in the type of the ink tank in which the negative pressure generating member containing chamber is disposed adjacent to the ink containing chamber. As a result, it has been found that the amount of the ink moving to the negative pressure generating member from the ink containing chamber is regulated because the supply of the ink in the ink containing chamber to the negative pressure generating member containing chamber is performed with the introduction of gas.
Furthermore, as a result of further analysis, a reverse conception different from the conventional conception has been obtained that the expansion of the air present in the ink containing chamber by the external environmental change cannot be stopped but the expansion of the air in the ink containing chamber is permitted in the ink containing chamber.
The present invention has been developed as a result of the present inventors further intensive studies based on the above-described finding, and an object is to provide a liquid supply system in the type of ink tank constituted of a negative pressure generating member containing chamber disposed adjacent to an ink containing chamber, in which the residual amount of liquid in a liquid containing portion able to generate a negative pressure by deformation can be known, and particularly in which a user can know the time to exchange the liquid containing chamber when the liquid containing chamber can be exchanged.
Another object of the present invention is to realize a more stable liquid supply operation by detecting a liquid condition in a liquid containing portion particularly in a liquid supply system in which the liquid containing portion is of a exchangeable type.
To achieve the above-described objects, according to the present invention, there is provided a liquid supply system which comprises a negative pressure generating member containing chamber provided with a liquid supply portion for supply liquid to the outside and an atmosphere connecting portion for connecting with atmosphere for containing a negative pressure generating member holding the liquid inside; a liquid containing chamber connected to the negative pressure generating member containing chamber, forming a substantially sealed space except the connection, and having a liquid containing portion which can generate a negative pressure by deformation; and liquid residual amount detecting means for detecting a liquid level position of the liquid in the liquid containing portion to detect the liquid residual amount in the liquid containing portion.
According to the above-described liquid supply system, the liquid containing portion is deformed so as to keep a balance of negative pressure with the negative pressure generating member containing chamber, lessens the influence of the environmental change, smoothly supplies the liquid to the negative pressure generating member containing chamber, and detects the liquid level position of the liquid in the liquid containing portion, so that the ink residual amount can steadily be detected. Particularly, when the outside air is introduced into the liquid containing portion with the introducing of the liquid out of the liquid containing portion during the gas-liquid exchange, the deformation of the liquid containing portion is determined by the negative pressure characteristic of the liquid containing portion, and the deformation amount of the liquid containing portion does not largely change. Therefore, as compared with when the liquid residual amount is detected from the deformation degree of the liquid containing portion, the stability of the residual amount detection is further enhanced.
As the liquid residual amount detecting means, optical detecting means utilizing a light absorption or scattering change when light is transmitted through the liquid, electrostatic capacity detecting means utilizing an electrostatic capacity change of a liquid container containing the liquid, and the like can be used.
According to the present invention, there is provided a liquid residual amount detecting method for detecting a liquid residual amount in a liquid containing chamber of a liquid supply system comprising a negative pressure generating member containing chamber provided with a liquid supply portion for supplying liquid to the outside and an atmosphere connecting portion for connecting with atmosphere for containing a negative pressure generating member holding inside the liquid, and the liquid containing chamber connected to the negative pressure generating member containing chamber and having a liquid containing portion forming a substantially sealed space except the connection and able to generate a negative pressure by deformation. The method comprises: a first liquid supply step of deforming the liquid containing portion to generate the negative pressure and reducing the volume of the liquid containing portion, and moving the liquid in the liquid containing portion to the negative pressure generating member to supply the liquid to the outside without introducing outside air into the liquid containing portion from the atmosphere connecting portion via the negative pressure generating member containing chamber; a second liquid supply step subsequent to the first liquid supply step of introducing the outside air to the liquid containing portion and causing gas-liquid exchange to move the liquid in the liquid containing chamber to the negative pressure generating member containing chamber so that the liquid is supplied to the outside; and a liquid level position detecting step of detecting a liquid level position of the liquid in the liquid containing portion during the second liquid supply step to detect the liquid residual amount in the liquid containing portion.
According to the above-described liquid residual amount detecting method, since the liquid level position of the liquid in the liquid containing portion is detected during the second liquid supply step of performing the gas-liquid exchange between the liquid containing portion and the negative pressure generating member containing chamber to supply the liquid to the outside, the residual amount of the liquid in the liquid containing portion can steadily be detected as described above.
According to the present invention, there is provided a liquid residual amount detecting method for detecting a liquid residual amount in a liquid containing chamber of a liquid supply system comprising a negative pressure generating member containing chamber provided with a liquid supply portion for supplying liquid to the outside and an atmosphere connecting portion for connecting with atmosphere for containing a negative pressure generating member holding inside the liquid, and the liquid containing chamber detachably connected to the negative pressure generating member containing chamber and having a liquid containing portion forming a substantially sealed space except the connection and able to generate a negative pressure by deformation. The method comprises: a liquid level position detecting step of detecting a liquid level position of the liquid in the liquid containing portion at a predetermined time interval in a period when no liquid is supplied to the outside from the negative pressure generating member containing chamber; and a suction step of forcibly sucking a part of the liquid held by the negative pressure generating member from the liquid supply portion after the liquid containing portion is exchanged when a difference between the liquid level position detected in the liquid level position detecting step and the liquid level position detected in the previous liquid level position detecting step is lower than a predetermined value.
In the liquid supply system provided with the liquid containing chamber having the liquid containing portion which can generate the negative pressure by the deformation, also when no liquid is supplied to the outside from the negative pressure generating member containing chamber, the liquid is moved between the negative pressure generating member containing chamber and the liquid containing chamber by the environmental change, and the like. For example, when the liquid is guided to the negative pressure generating member containing chamber out of the liquid containing portion, and it is judged that the residual amount of the liquid in the liquid containing portion is reduced, the liquid containing chamber is exchanged as it is. Then, when the exchanged liquid containing chamber and the negative pressure generating member containing chamber are balanced in inner pressure, the liquid is excessively guided out of the new liquid containing chamber, and the liquid possibly leaks from the liquid containing portion of the negative pressure generating member containing chamber. In this case, like in the above-described liquid residual amount detecting method, also when no liquid is supplied to the outside from the negative pressure generating member containing chamber, the liquid level position of the liquid in the liquid containing portion is detected. When it is judged that the result has a less residual amount by a certain value or more than the previous result, the leakage of the liquid from the liquid containing portion after the exchange of the liquid containing chamber is securely prevented by forcibly sucking a part of the liquid from the liquid supply portion after the exchange of the liquid containing chamber.
Additionally, in the specification, the negative pressure generating member container and the liquid container are used when the containers can be separated from each other, and the negative pressure generating member containing chamber and the liquid containing chamber are used not only when they can be separated but also when both are constantly integrally disposed.
Moreover, the region unfilled with the liquid in the vicinity of the atmosphere connecting port of the negative pressure generating member containing chamber is used as a term including not only a space (buffer portion) provided with no negative pressure generating member as described later but also a case in which the negative pressure generating member is present but no ink is supplied.